Collaborative Research: Seismicity of the Equatorial Mid-Atlantic Ridge and its Large Offset Transforms

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The sizes and locations of earthquakes recorded by eight hydrophones moored in the Equatorial Atlantic Ocean provide an unparalleled view of the seismicity of the poorly understood slow-spreading Mid-Atlantic Ridge in this region. The data also allow testing of the idea that earthquakes can be predicted at ocean transform faults, and they provide insight into how triple junctions (where three tectonic plates meet) work. The Equatorial Atlantic seafloor has not been studied extensively but is interesting for many reasons. First, the Mid-Atlantic Ridge axis is offset on some of the longest transform faults in the oceans. As an example, the Romanche transform is greater than 900 km long. In places, the transform offsets are so large that the total length of the transform faults is longer than the total length of the ridge axis. These fracture zones are extremely rugged, are important conduits for bottom water moving between the North and South Atlantic Ocean, and probably act as physical barriers blocking the transport of hydrothermal vent fauna along the ridge axis. The Equatorial Atlantic transforms are ideal for testing the short-term predictability of earthquakes at ocean transform faults and the results may help in understanding earthquakes on continental faults. A second interesting aspect of the region is that it contains the triple junction where the North America, South America, and Africa tectonic plates meet. The exact location of the triple junction is still a matter of debate, and this study will help to define its location. Third, the location of the plate boundary between the North America and South America plates is not known even though there is motion between the plates. The earthquakes recorded by the hydrophones provide important new information about the motion of these two plates, and how and where that motion is taking place. The hydrophone array also records a variety of natural and man-made noises and will facilitate a wide-range of studies beyond the scope of the proposed work. Examples include the use of ambient sound measurements to study various climate research topics, including estimating wave heights, rainfall intensity and wind speed during hurricanes. In addition, recorded whale vocalizations allow the distribution and migration of these animals to be tracked throughout the Equatorial Atlantic Ocean.